GB2380246A

GB2380246A - Moisture removal from refrigerant

Info

Publication number: GB2380246A
Application number: GB0123107A
Authority: GB
Inventors: Mohammed Amin
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-09-26
Filing date: 2001-09-26
Publication date: 2003-04-02
Anticipated expiration: 2021-09-26
Also published as: GB0123107D0; GB2380246B

Abstract

A moisture trap (20) is connected between a liquid refrigerant reservoir (13) and a compressor (11) or suction line (18) of any conventional refrigerator system without affecting operation of the latter. Liquid refrigerant enters the trap housing (20) via a capillary tube (21), or via an evaporator valve and vaporises as it enters. The trap housing (20) is either filled with a metal mesh/gauze or has an evaporator of an auxiliary refrigeration circuit mounted therein, so that any moisture is deposited as ice on the mesh or the evaporator. After a period of time, e.g. 12-24 hours, during which the refrigerant passes several times through the trap (20), said trap (20) can be disconnected. The ice therein is melted and water and any oil residue which has accumulated are removed.

Description

MOISTURE REMOVAL FROM REFRIGERANT This invention concerns a device, which may be termed a moisture trap, for connection between two locations in a refrigerant circulation system for removal of moisture from the refrigerant.

The presence of moisture in refrigerant, which circulates in a closed system in commercial refrigeration apparatus e. g. in warehouses, supermarkets, distribution depots etc, is a common problem. Moisture tends to enter the system whenever pipes or gauges are connected or replaced or repaired such that moisture laden ambient air can gain access. Often a few mls of water are present in a system containing, for example, 20Kg of refrigerant. If the water collects and freezes it can cause pipes to split (specifically the evaporator coil) or valves to become blocked. It can also lead to corrosion of compressor windings. Thus it can lead to reduced efficiency of the cooling effect of the system or in the power consumed, and sometimes to failure of the system.

Filter driers are commonly fitted into refrigerant circulation systems in order to hold moisture. However, they are not always changed frequently enough if at all, may not hold all

the moisture which has accumulated in a system, and may release their moisture content back into the system at some stage.

An object of the present invention is to provide a device which can be connected to a refrigerant circulation system for a relatively short period, to remove moisture therefrom, without having to shut down and/or drain the system-which is troublesome and costly.

With this object in view, the invention provides a device comprising a housing having an inlet in the form of a capillary tube or expansion valve such that liquid refrigerant entering the housing therethrough will vaporise within the housing, and also an outlet, and said housing containing a material of high surface area and good heat conducting properties.

The material within the housing may suitably comprise a mass of steel mesh or any other metal (e. g. aluminium) of mesh or perforate form, which is folded or crumpled. All that is essential is that a large surface is provided onto which any moisture within the refrigerant can be deposited as ice, as the vaporisation of the refrigerant removes heat from the interior of the housing. After disconnection of the device, the ice is then melted and removed.

A low power heating element may be provided around at least part of the exterior of the housing to ensure that all the

refrigerant substance vaporises rapidly and remains as a vapour until it is drawn back into the circulation system of the refrigerator.

As an alternative to a mass of material of high surface area and good conductivity, or in addition thereto, the device of the invention may include an auxiliary refrigeration system having evaporator means mounted inside the housing, as a low temperature element facilitating the freezing of any moisture, and compressor and condensing means mounted outside the housing. In this respect, a discharge conduit from the condensing means may suitably serve as heating means on the exterior of the housing, for the purpose mentioned above.

The invention also provides a corresponding method of removing moisture from a refrigerant circulation system by connecting a device as claimed in any preceding claim to the system so as to allow liquid refrigerant to leave the system at a first location and enter the device via the capillary tube or expansion valve which causes it to evaporate within the device, and leads to any moisture therein forming a deposit of ice upon the material and/or upon the evaporator means within the housing, and so as to allow refrigerant vapour to return to the system at a second location, which is upstream of the first location, disconnecting the device after a period of time, allowing any ice to melt, and emptying the device of moisture.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a refrigerant circulation system to which a device in accordance with the invention has been connected; Figure 2 is a diagrammatic cross section of a first embodiment of the device of the invention; Figure 3 is a similar view of a second embodiment of the device of the invention; and Figure 4 is a similar view of a third embodiment of the device of the invention.

Refrigerants used in commercial and domestic refrigeration systems are chlorofluorocarbons, hydrochlorofluorocarbons, or hydrofluorocarbons, or any blend of these three types of

compounds. They all have boiling points in region of-20 C to - 5 C, so are gases at 0 C or above, unless held under pressure. The refrigerant circulation system shown in Figure 1 is a basic system, which would apply to all these refrigerants or any blends. Likewise, the device and method of the invention are applicable to all such systems (or more complex ones) and all these refrigerants or any blends thereof.

The basic system 10 consists of a compressor 11, a condenser 12, a liquid reservoir 13, a liquid drier 14, and sight glass 17, an expansion device 15 and an evaporator 16.

The refrigerant circulates in the direction shown by the arrows and it is the evaporator 16 which cools down the space inside the refrigeration apparatus, in which food or other perishable goods are stored. The sequence as the refrigerant circulates is as follows: The compressor 11 compresses low-pressure low temperature vapour refrigerant to high-pressure high temperature vapour.

The condenser 12 turns high-pressure high temperature vapour to high-pressure low temperature liquid.

The liquid reservoir 13 receives and stores liquid refrigerant until it can be used by the system.

The liquid line drier 14 is a filter which holds moisture and the sight glass 17 allows inspection of the liquid level.

In the expansion device 15 the liquid refrigerant passes through a small orifice which causes a pressure drop and makes the liquid refrigerant boil off.

The evaporator 16 is where the liquid refrigerant is boiling off, cooling the surround space and product in the process.

The refrigerant vapour is then sucked back to the compressor 11 through a suction line 18 as a low temperature low-pressure vapour.

The moisture trap device in accordance with the invention comprises a housing 20 having an inlet line 21, which is in the form of a capillary tube and an outlet line 22. The capillary tube 21 is connected to a conventional connection port provided in the liquid reservoir 13. The outlet line 22 is connected to a suction port of the compressor 11 or any other available suction port in the system 10 so that refrigerant vapour will be sucked back from the device into the main system 10.

In a simple embodiment, illustrated in Figure 2, the housing 20 is in the form of a steel box which is filled with a mass of steel mesh 24 and has a low power heating element 26 mounted externally to one or more wall, or wrapped around the housing.

In a more complex embodiment, illustrated in Figure 3, the housing 20 is again in the form of a steel box having a capillary inlet 21 intended for connection to the liquid reservoir 13 and an outlet 22 intended for connection a suction port of the system from which moisture is to be removed.

However, an auxiliary refrigeration system also having the same

basic, conventional circuit is provided, of which an evaporator 34 is mounted inside the housing 20. An inlet line 31 from a condensing unit (not shown) of the auxiliary system leads into the evaporator 34, and an outlet line 32 leads back from the evaporator 34 to the condensing unit. Either discharge piping from the condensing unit or a separate low power heater 36 is mounted to or wrapped around the housing 20.

Wire mesh (not shown) preferably fills the space inside the housing 20, around the evaporator 34. However, this may not be necessary in some embodiments. The mesh helps to catch and hold moisture inside the trap 20 by providing surface for it to freeze to until it can be removed by subsequent melting.

In a third embodiment, shown in Figure 4, the housing 20 of the moisture trap has two chambers 23,25, connected by a pipe 27.

The inlet to the first chamber 23 is fitted with an expansion valve 28 which may take the place of a capillary tube in causing the incoming refrigerant liquid to vaporize owing to the pressure drop encountered upon entering the chamber 23.

Heaters 26 are provided external to both chambers 23,25, and both the chambers and the connecting pipe 27 are filled with steel wire mesh 24, as in the first embodiment. The purpose of this construction is that the second chamber 27 should, with its extra heater 26, more reliably prevent liquid returning to the main refrigeration system 10.

The purpose of the heaters 26,36 is to ensure that the refrigerant is completely vaporised, and is vaporised quickly enough to bring about the local cooling required to cause deposition of frozen moisture and also to be rapidly sucked back to the main system.

Detailed procedure for use of a moisture trap of the invention, as shown in Figures 2 or 3 or variants thereof is as follows: Firstly, the housing 20 should be clean and dry before use, and this should be checked. The capillary tube or tubes 21 is/are then fitted to the housing 20 and the liquid receiver 13 of the refrigeration system and the suction hose or hoses 22 are fitted between the housing 20 and the suction port or suction line of the system. The housing 20 should ideally be evacuated or purged to remove nitrogen or air, before these lines 21,22 are opened.

The heater for heat only traps or the condensing unit for selffreezing traps are then switched on. Finally, the liquid receiver (13) port to the trap, and the suction port to the system are opened and the trap is working.

The trap should be left connected and switched on overnight if possible. Twelve to twenty four hours should be sufficient.

In order to remove the trap, the first step is to close the liquid receiver (13) port, but not yet disconnect it to prevent refrigerant leaking to atmosphere. The heaters and/or the trap condensing unit should be left switched on. The liquid refrigerant still in the trap will then continue to boil off.

After about ten minutes any remaining liquid should have turned to vapour in the trap and the main system can be placed on pump down to remove vapour from the suction side of the system.

This will remove the vapour from the trap. Alternatively, the suction valve can be front seated to suck the vapour from the trap back into the system, or a recovery unit can be used to remove the vapour from the trap after closing all ports. The trap heaters and/or condensing unit can then be switched off and the suction outlet from the trap to the system closed. A pressure gauge should now be fitted to the trap. If pressure is rising the trap should not be opened as it means there is still liquid inside the trap. If pressure stays constant, Opsi or below, wait fifteen to twenty minutes before opening the trap. It is best waiting before opening the trap to allow the inside of the trap to warm up. This will ensure that no moisture from the surrounding air will condense on the inside of the trap.

Upon opening the trap there will be a lot of dirt and oil mixed, and also white blobs which are moisture mixed with oil.

The oil may be drained into a can or if there is only a small amount it can be wiped clean with a cloth or tissue. The wire

mesh (also known as gauze filters or moisture retainers) should be washed in washing-up liquid and hot water then thoroughly dried and replaced. Alternatively, new ones can be fitted for subsequent use of the trap. The trap should then be warmed up with a brazing torch to ensure that there is no more moisture in the trap, then closed and sealed. The trap can be pressurised with nitrogen (10-20psi) or evacuated and stored until needed again.

It is particularly advantageous that operation of the moisture trap of the invention does not require the shutting down of the refrigerating system from which moisture is to be removed.

Indeed, it does not affect the continued operation of the refrigerating system in any significant way, so is a costeffective way of servicing the system to remove moisture and obtain greater efficiency in the long run.

Claims

CLAIMS 1. A device for connection between two locations in a refrigerant circulation system for removal of moisture therefrom, said device comprising a housing having an inlet in the form of a capillary tube or expansion valve such that liquid refrigerant entering the housing therethrough will vaporise within the housing, and also an outlet, and said housing containing a material of high surface area and good heat conducting properties.
2. A device according to claim 1 wherein the material contained within the housing comprises steel mesh.
3. A device according to claim 1 or 2 wherein heating means are mounted to the exterior of the housing.
4. A device for connection between two locations in a refrigerant circulation system for removal of moisture therefrom, said device comprising a housing having an inlet in the form of a capillary tube or expansion valve such that liquid refrigerant entering the housing therethrough will vaporise within the housing and also an outlet, and an auxiliary refrigeration system of which

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evaporator means are mounted inside the housing and the remainder is provided externally of the housing.
5. A device according to claim 4 wherein heating means are mounted to the exterior of the housing.
6. A device according to claim 5 wherein the heating means comprises a discharge conduit from condensing means of the auxiliary refrigeration system.
7. A device according to claim 4,5 or 6 wherein a material of high surface area and good heat conducting properties surrounds the evaporator means within the housing.
8. A device for removal of moisture from a refrigerant circulation system substantially as hereinbefore described with reference to and as illustrated by Figures

3 Or 4 0 ''rnr'ri\7'i''r) rr rTn7nrc ;

8. A method of removing moisture from a refrigerant circulation system by connecting a device as claimed in any preceding claim to the system so as to allow liquid refrigerant to leave the system at a first location and enter the device via the capillary tube or expansion valve which causes it to evaporate within the device, and leads to any moisture therein forming a deposit of ice upon the material and/or upon the evaporator means within the housing, and so as to allow refrigerant vapour to return to the system at a second location, which is upstream of the first location, disconnecting the device

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after a period of time, allowing any ice to melt, and emptying the device of moisture.

9. A device for removal of moisture from a refrigerant circulation system substantially as hereinbefore described with reference to and as illustrated by Figures 2,3, or 4 of the accompanying drawings.

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An, ended claims have been filed as follows

CLAIMS 1. A device for connection between two locations in a refrigerant circulation system for removal of moisture therefrom, said device comprising a housing having an inlet in the form of a capillary tube or expansion valve such that liquid refrigerant entering the housing therethrough will vaporise within the housing, and also an outlet, and said housing containing a mass of metal of mesh or perforate form and having good heat conducting properties.

2. A device according to claim 1 wherein the material contained within the housing comprises steel mesh.

3. A device according to claim 1 or 2 wherein heating means are mounted to the exterior of the housing.

4. A device according to claim 1,2 or 3 further comprising an auxiliary refrigeration system of which evaporator means are also mounted inside the housing and the remainder is provided externally of the housing.

5. A device according to claim 3 and 4 wherein the heating means comprises a discharge conduit from condensing means of the auxiliary refrigeration system.

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6. A refrigerant circulation system comprising a circuit of

-)- t' f iTr'infoTrt QtTf'c:conctedin ec 1 **'n n-r-l 5 compressor, a condenser, a liquid reservoir, a liquid drier, an expansion device and an evaporator, and a device according to any preceding claim connected, in parallel to the aforesaid circuit, between the liquid reservoir and either the evaporator or the compressor inlet so that refrigerant is passed through the device from the liquid reservoir and returns to the circuit at or near the evaporator or the compressor inlet.

7. A method of removing moisture from a refrigerant circulation system by connecting a device as claimed in any preceding claim to the system so as to allow liquid refrigerant to leave the system at a first location and enter the device via the capillary tube or expansion valve which causes it to evaporate within the device, and leads to any moisture therein forming a deposit of ice upon the material and/or upon the evaporator means within the housing, and so as to allow refrigerant vapour to return to the system at a second location, which is upstream of the first location, disconnecting the device after a period of time, allowing any ice to melt, and emptying the device of moisture.

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